ELISA reactions and other simple immunoassays are commonly used for diagnosing disease. Many assays are configured to detect a single analyte. Therefore, when several differential diagnoses are possible, several different such assays are often conducted in parallel.
Existing approaches for broadly characterizing an immune response involve multiple standard ELISAs, use of library panning involving multiple rounds of selection, or printing of known proteins from pathogens or host proteins in an array format to detect antibodies to pathogens or autoantibodies. T-cells and B-cells have also been characterized by isolating and cloning specific regions of the T- and B-cell genome to sequence the recombination event. All of these processes are labor intensive and take time. They are not conducive to a standard clinical diagnostic protocol or early detection before specific analytes for which specific binding reagents are provided.